Objective: This controlled pilot study was designed, first, to examine the efficacy of two different group therapy formats for schizophrenia and schizoaffective patients: a patient-centred, psychoeducative and coping-orientated group therapy approach and a supportive therapy group. Secondly, it intended to establish preliminary hypotheses on the therapeutically relevant factors. Method: In a sample of 32 patients suffering from schizophrenia or a schizoaffective disorder the effect sizes of the coping-orientated therapy approach and a supportive group therapy on several outcome variables were examined and the predictive power of different effect variables on outcome was analysed. Results: The effect sizes show improvements in the cognizance of the disorder and the related pharmacotherapy, the psychopathology and the social functioning for both therapy conditions. Moreover, outcome as measured after I year was best predicted by the patient's mastery of active. problem-focused coping strategies. Conclusion: The results corroborate the appropriateness of focusing on aspects of coping-behaviour in psychological interventions.